Lever key



March 23, 1954 D. N. M D ONALD FIG. 2

INVENTOR. Duncan N. MacDonald Attorney Patented Mar. 23, i954 LEVER KEY Duncan N. MacDonald, Evanston,

111., assignor to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application January 16, 1951, Serial No. 206,282

4 Claims.

This invention relates to telephone keys, and more particularly to what are known as ringi and listening keys.

The object of this invention is to provide a positive stop for a lever key at its center position in order to prevent overthrow of the key when it is suddenly released from one of its extreme positions, either listening or ringing, and the inadvertent disturbance of the circuits corresponding to the opposite position.

A feature of my invention is the provision of a notched cam body which operates, as a positive stop for the key.

Another feature of my invention is the provision of a weighted cantilever detent spring in the spring pileup which is deflected by the initial operation of the key in one direction and upon the release of the key suddenly, either by snap action or quick operation, from that direction, the detent spring restores beyond its normal position and engages the notches in the cam body and acts as a positive stop for the key, thus preventing the objectionable disturbance of the opposite position circuits.

Another feature of my invention is the provision of a spring of the above description in which the mass of the spring weight is of such a value that the key may be operated from one extreme position to the other in a deliberate manner without the positive stop action of the detent spring taking place. Thus the detent prevents overthrow but does not prevent normal operation of the key.

It is a further object of my invention to produce an improved device of the class described which will embody these desirable features and advantages, all in a simple, efficient and economical manner.

These and other objects and features of the invention will appear from the detailed description which will be given below with reference to the accompanying drawings showing a preferred embodiment. In these drawings:

Fig. 1 is a side elevation of the inventionwith the cam in its normal position.

Fig. 2 is a right end view of Fig. 1.

Fig. 3 is a partial side elevation of the invention with the cam in one of its extreme positions, either ringing or listening.

Fig. 4 is a partial side elevation of the invention with the cam almost restored to normal with the detent spring past normal and in engagement with the notch in the cam body.

Referring now in detail to my invention as illustrated, the preferred form of my key comprises two T-shaped frame members 2, suitably fastened to an escutcheon plate I at one end, extending downward in a parallel relationship and clamped in a suitable manner by two L-shaped clamps l1 and a spacer, not shown. Mounted upon the clamps I1 and extending right and left from the frame members 2 are a plurality of springs approximately parellel to the fram members 2, suitably insulated from each other and the frame members in an arrangement usually known as a spring pileup. In this embodiment four such pileups are shown, two with detent springs, such as H), and two without, but any number without detents may be used consistent with the size of the key, and since all pileups perform in substantially the same well-known manner, with the exception of the detent springs, the description of one containing a detent spring will sufiice for all. In such a pileup are contact springs l5 and I9, back contact springs I6 and I4, lever spring 8 which is also a cam follower, lever spring Ill which also acts as the positive detent, a bushing 9 for transmitting force from spring 8 to spring l0, lever spring l3, and bushing l3 performing a similar function between springs l0 and I3. Mounted pivotally between the frame members 2 is a cam 3, which also extends through a slot in the escutcheon plate I. Atop the cam body on a threaded projection is a handle or grip 4 of suitable insulating material. Diametrically opposed to the handle 4 beneath the escutcheon plate and between the frame members 2 are a pair of cam rollers 5 mounted rotatably on the cam body, one on either side thereof. The cam rollers 5 are acted upon by the cam follower springs 8 so as to hold the handle 4 in a vertical central position, which is the normal position of the key. In this normal position the detent spring I0 is also in its normal position at rest just beyond the circumference of the cam body. The buffer or bushing 9 afiixed to the follower spring 8 does not at this time rest against the surface of the detent spring l0 but a clearance exists between these two members. Bushing I2 ailixed to lever spring l3 rests lightly against the detent spring I0 but does not diminish the required clearance. Slightly below the horizonal diameter of the cam body portion and at the circumference thereof are two notches 1, suitably hardened, of a depth slightly greater than the guage of the detent spring. In this normal position of the key certain electrical circuits exist through the made contacts on the lever and contact springs, and certain other electrical circuits are incomplete due to the open condition of other contacts on these springs.

Operation of the key to control the various circuits is performed manually by means of the handle 4. Movement of the handle to the left as shown in Fig. 3 correspondingly moves the cam rollers to the right and deflects the entire spring pileup by deflecting first cam follower spring *8, which moves through the clearance space to contact detent spring III thereupon deflecting it with the subsequent motion of the cam. Bushing l2, resting lightly upon detent spring ID, thereupon causes lever spring l3 to follow the cam motion also. At the extreme right position of the cam roller springs 8, and I3 make contact with springs l6 and I4 respectively, to control certain electrical circuits. The cam roller is self-locking in this position since the cam follower spring 8 has travelled beyond the dead center position of the cam roller 5. In this position the circuits on the opposite side of the key are in their original state. Release of the key from this position is also performed manually, and the action of the detent spring is dependent upon the character of the manual force applied. lhe typical method of release by an attendant is to allow the key to snap back to its normal position. In such an instance the positive lock feature operates to prevent any overthrow of the key from deflecting the opposite pileup of lever and contact springs and the subsequent disturbance of the circuits controlled by them. Operation of this feature is as follows: The cam 5 ismoved through its dead center posi-- tion on the cam follower spring a by the flick or snap given it by the attendant and is returned toward its normal position by the action of the follower spring 8 The detent spring It] follows the return of the follower spring 3 until the normal position of the cam roller is neared. This position is illustrated by Fig. 4, At this point the inertiaof'the end of the detent spring is such that it overcomes the resiliency of the. spring itself and returns past its normal position to engage the notch on the cam body 3. In this position clearance which existed between bushing 53 and spring in in Fig. 1 no longer exists. The engagement of the detent spring Hi, and the notch 1 occurs just before the cam roller 5 strikes the opposite cam follower spring IS. The inertia then being absorbed in stopping the cam motion, the resiliency of the spring It then lifts the detent edge from the notch I and the roller 5 is returned to normal by the further action of the cam follower spring 8. pushing it against the other cam follower spring l8 where it is retained in its vertical position. This further travel of the cam roller 5 is not sufficient to cause deflection of the follower spring l8 as it comes to rest against it, and therefore does not disturb any circuits controlled by the left spring pileup. The key is now in the position shown in Fig. l, and is ready for further operation.

Deliberate operation of the key from one extreme position to the other extreme position does not cause the detent spring iii to engage the-cam body 5 and prevent this operation. The detent spring [0 does not gather the momentum necessary to cause it to travel beyond its normal position under the influence of the weight ,and it merely returns. to its normal position where it clears the cam body 3. The handle then may continue in its travel to the opposite extreme position.

Having thus particularly described my invention what I claim and desire to be protected by issuance of Letters Patent is:

1. In an. operators key, means for operating and releasing said key, a cam pivotally mounted therein, shoulders on said cam, a plurality of detent springs, said detent springs fixedly mounted at one end in said key, said detent springs free at the other end and each having a weight mounted on the free end thereof, said free ends positioned closely to said shoulders but out of engagement therewith, means for deflecting one of said springs when said key is operated in one direction, other means for deflecting another of said springs when said key is operated in the other direction, said spring operating under the influence of said weight thereon to return past its original position to engage one of said shoulders to prevent overthrow thereof when said key is suddenly released from said one direction, said spring restoring directly to its original position close to said shoulder when said key is slowly released from said one direction, the operation to release said key in the said other direction being substantially similar.

2. In a switch key, a frame, a notched cam pivotally mounted on said frame, a cam. roller rotatably mounted on said cam, operating and releasing means projecting from said earn, a plurality of springs mounted on said frame. in a stratified arrangement, a follower spring in said arrangement resting against said cam roller, said follower spring being displaced upon operation of said operating means, a detent spring in said arrangement normally out of the path of said notch, a weight on the free end of said detent spring, means for displacing said detent spring upon operation of said operating means, locking means including said cam roller and said follower spring for maintaining said cam in an extreme operated position, said releasing means operating to release said locking means, said follower spring operating against said cam roller to return said cam toward its original position, said detent spring operating under the influence of said weight thereon to return past its original position to engage said notch on said cam and arrest the motion thereof, said detent spring disengaging said notch and moving 0 t of the path thereof under the influence of the internal tension there-- in after the motion is arrested, said cam returning to its original position under the further infinance of said follower spring.

3. In a key switch, the combination with anoperating device having notches thereon, of a pair of cantilever detent springs controlled thereby each having a normal and an operated position, said device having means for deflecting one of said detent springs upon movement of said key from oneposition to another, each of saiddetent springs having a weight mounted on the free end thereof, each of said detent springs operating under the influence of said weight thereon to return past its normal position to engage one of the notches on said notchedd'evice upon sudden return of said notched device from the-oppositepositions to which it has beenmoved by said key, each spring returning directlyto its normal position of non-engagement upon the slow return of said key from opposite positions without engaging said notched device.

4. In an operators key, means for operating and releasing said key, a cam pivotally mounted therein, shoulders on said cam, a plurality of detent springs, said detent springs fixedly mounted at oneend of said hey, saiddetent springs free at the other end, said free ends positioned closely to saidshoulders but out of engagement therewith, means for deflecting oneof saidsprings whamuekl key is operated in one direction, other means for deflecting another 01' said springs when said key is operated in the other direction, said spring being thereby constrained, said spring having an inherent mass such that when suddenly released by the sudden release of said key from said one direction it accelerates under the inherent restoring forces present due to the strained condition thereof, said spring thus acquiring a velocity producing a kinetic energy sufiicient to overcome the restraining forces tending to keep the spring rigid, thereby overriding its normal position to a position of engagement with the shoull ders of the cam,

6 said spring restoring directly to its original position close to said shoulder when said key is slowly released from said one direction, the operation of releasing said key in the said other direction being substantially similar.

DUNCAN N. MACDONALD.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,508,798 Klay Sept. 16, 1924 2,427,187 Bosh Sept. 9, 1947 

